Method of manufacturing envelopes for cathode-ray tube

ABSTRACT

Method of manufacturing envelopes for cathode-ray tubes, in particular for oscillograph tubes, in which first a cone having a cylindrical and a rectangular end is formed by sealing together two identical pre-shaped dishes of mirror plate, after which a neck composed of tubular glass is sealed to the cylindrical end of the cone and a rectangular screen of mirror plate is sealed to the rectangular end.

United States Patent Verhoeven et al.

METHOD OF MANUFACTURING ENVELOPES FOR CATHODE-RAY TUBE Inventors: Adrianus Cornelis Johannes Verhoeven; Johan Josephus Hendricus Bogaard; Jan Peper, all of Emmasingel, Eindhoven, Netherlands U.S. Philips Corporation, New York, NY.

Filed: Aug. 11, 1972 Appl. No.: 279,970

Assignee:

Foreign Application Priority Data Aug. 13, 1971 Netherlands .1 7111167 US. Cl 65/42, 65/55, 65/58 Int. Cl C03b 23/24 Field of Search 65/40, 42, 55, 58, 107;

220/2.l A, 2.3 A

Oct. 1, 1974 156] References Cited UNITED STATES PATENTS 1,787,460 1/1931 Wilcox 65/55 X 2,680,332 6/1954 Young 65/40 2,699,014 1/1955 Van Steenis...... 220/21 A 3,369,881 2/1968 Bennett et al. 65/58 Primary Examiner-Arthur D. Kellogg Attorney, Agent, or Firm--Frank R. Trifari [57] ABSTRACT Method of manufacturing envelopes for cathode-ray tubes, in particular for oscillograph tubes, in which first a cone having a cylindrical and a rectangular end is formed by sealing together two identical pre-shaped dishes of mirror plate, after which a neck composed of tubular glass is sealed to the cylindrical end of the cone and a rectangular screen of mirror plate is sealed to the rectangular end.

4 Claims, 10 Drawing Figures Pmwnznucr 1mm sum aor 5 Fig.5

mum mu 3.839.082 SHEET 50F 5 Fig.9

METHOD OF MANUFACTURING ENVELOPES FOR CATHODE-RAY TUBE The invention relates to a method of manufacturing envelopes for cathode-ray tubes, in particular for oscillograph tubes, in which pre-shaped glass elements are sealed together to form an envelope having a neck, a cone with at least partly rectangular cross-section and a rectangular screen.

In such a known method, an envelope body comprising the cone and the neck and having a rectangular cross-section throughout the length is composed of two halves so that it is possible that two oppositely located walls of the envelope body extend in parallel; this latter is not possible in manufacturing an envelope body consisting of one single part in connection with the removal of such a body from the press mould.

It is the object of the invention to provide a method which enables the series production in different numbers in a very simple and economical manner of envelopes having varying dimensions and shapes.

According to the invention this object is mainly achieved in that by sealing together elements of mirror plate first a cone having a rectangular and a cylindrical end is formed, after which the envelope is composed by sealing together a tubular element, which forms the neck, to the cylindrical end and a rectangular plane mirror plate, which forms the screen, to the rectangular end.

By starting from elements of mirror plate for the cone, from a tubular element for the neck, and from a piece of plane mirror plate for the screen, it is possible to compose the envelope in a very cheap manner from standard products which are obtainable in a variety of dimensions.

The cone of the envelope obtained by the method according to the invention has a uniform wall thickness which can be varied in a simple manner by starting from mirror plate having a different thickness; for the screen and the cone the same type of mirror plate may be used.

The cone may be composed, for example, of four elements, one for each side of the cone, only a small preshaping of the elements being necessary. In a preferred embodiment of the method according to the invention, however, the cone is formed by melting two identical dishes together which are obtained by cutting plates with a desired circumference from a flat mirror plate and then positioning them on a convex mould, after which the plates and the mould are heated at such a temperature that the plates sag around the mould and engage the surface thereof, the dishes thus formed being ultimately cooled to room temperature and each time two dishes being welded together to form a cone.

In contrast with the expensive pressing process in which inter alia a glass furnace for melting the glass is necessary, only a simple mould and furnace are required for carrying out the method according to the invention; moulds for the production of newly designed envelopes and cones can be manufactured in a minimum of time. An after-treatment of the dishes is not necessary. Moreover it is possible in a simple manner to manufacture envelopes of complex shapes, for example, envelopes having a double cone the crosssection of which decreases towards the two ends, or envelopes having a cone the cross-section of which at the same end increases in one direction and decreases in the other direction.

A cone of the accurate desirable shape and dimensions is obtained in a further preferred embodiment of the method according to the invention in that for welding two dishes together they are centered in a mould relative to each other in such manner that their edges to be welded together contact each other, after which the edge portions of the dishes are: heated by means of burners until the glass of the edge portions becomes electrically conductive after which they are further heated by means of thermal energy caused by the Joule effect until the edges are sealed together, the resulting cone being then cooled. The welding seams on the cone are proportionally narrow and show a uniform appearance so that an after-treatment of the welding seams is not required.

According to another preferred embodiment of the method according to the invention the dishes during welding together are moved relative to each other in a direction normal to their edges to be welded together. As a result of this measure, a solid welded joint having a uniform strength throughout the length of the welding seams is obtained.

The envelope manufactured by means of the method according to the invention is characterized by the tubular neck, by the cone which is composed of several elements and by the characteristic shape of the cone the rectangular cross-section of which on the side of the screen changes into a cylindrical cross-section on the side of the neck.

The invention will be described in greater detail with reference to an embodiment shown in the drawing. In the drawing:

FIG. 1 shows an envelope obtained by the method according to the invention,

FIG. 2 shows a mirror plate to be formed into a dish,

FIGS 3, 4 and 5 are a plan view, a side-elevation and a front elevation of a mould with a plate placed thereon,

FIG. 6 shows the mould with the deformed plate,

FIG. 7 is a perspective view of the shaped dish,

FIGS. 8 and 9 are a side elevation and a front elevation of a mould for welding the dishes together,

FIG. 10 shows a cone composed. of two dishes.

The embodiment relates to an envelope 1 to be manufactured by means of the method according to the invention and shown in FIG. 1 the cone 3 of which having a cylindrical end 5 and a rectangular end 7 is composed of two identical dishes 9. A tubular element 11 is sealed to the cylindrical end 5 and forms the neck 13 of the envelope 1. The screen 15 of the envelope is formed by a rectangular flat mirror plate 17 provided on the rectangular end 7.

For manufacturing the envelope 1, a smaller plate which is denoted in the drawing by 21 is cut from a flat mirror plate not shown. The dimensions and the circumference of the plate 21 are chosen to be so that said plate forms the development of the dish 9 to be formed and thus of half of the cone 3 divided in the longitudinal direction. The plate 21 is then positioned on a mould 23 and secured relative to the mould, for example, by means of clamps. This position is shown diagrammatically in FIGS. 3, 4 and 5. The shape and the dimensions of the part of the mould 23 serving for the design of the plate 21 are identical to the shape and the dimensions of the dish 9. The mould 23 and the plate 21 are then heated uniformly to the softening temperature of the glass, for example, by placing the mould with the plate in a furnace or by passing it through a continuous furnace. Such a furnace 25 is shown diagrammatically in FIG. 6. As soon as the glass has reached the softening temperature, the plate 21 deforms, gradually sags around the mould 23 and ultimately fully engages the surface of the mould, as is shown in FIG. 6. After cooling to room temperature, the dish 9 may be removed from the mould 23. The resulting dish 9 is shown in FIG. 7. It is obvious that for the manufacture of a single envelope or of a comparatively small number of envelopes one single mould is sufficient, each time one dish being formed. For the manufacture of a greater number of identical envelopes, two or more identical moulds may be used, several disher being formed simultaneously or continuously.

The cone 3 is obtained by welding two dishes 9 together. The mould 27 shown in FIGS. Sand 9 may be used for this purpose. This mould comprises two pairs of supports 29, 31 on which the two dishes 9 to be welded together are placed. The supports 29, 31 are secured so as to be adjustable to one end of two pairs of arms 33, 35. The other end of said arms is connected to rods 37 and 39, at least one of each pair of arms being pivotable relative to the associated rod. By means of a lever 41 the two arms 33 with the supports 29 can be adjusted relative to each other, while the arms 35 with the supports 31 are adjustable relative to each other by means of a lever 43. The rod 39 bears on a telescopic supporting column 45 which is secured to a base plate 47. The rod 37 is slidably journalled relative to the supporting column 45 and can be moved up and down by means of a lever 49. Two fixed pins 51 serve for guiding the rod 37.

For welding two dishes 9 together to form a cone 3, the dishes are placed on the supports 29 and 31 in such manner that the longitudinal edges 53 and 55 of the dishes 9 extend in parallel and contact each other. The edge portions of the dishes 9 are then pre-heated by means of burners 57 until the glass of said edge portions becomes electrically conductive. The edge portions are then heated further by means of thermal energy caused by the Joule effect. For this purpose, current is conveyed through the pre-heated edge portions by means of two pairs of electrodes 59 and 61 until the edges 53, 55 of the two dishes 9 are sealed together. During the melting together, the two dishes are periodically moved relative to each other in a direction normal to their edges to be welded together. For that purpose, the rod 37 with the arms 33 and the support 29 is moved up and down by means of the lever 53 with a very short stroke. After melting their edges together,

the two welded dishes 9 are cooled and removed from the mould 27. FIG. 10 shows the resulting cone 3 of which the welding seams 63 have a uniform appearance. Any after-treatment of the welding seams has been found to be unnecessary.

A tubular element 11 which has been pretreated in known manner, is composed of tubular glass and will form the neck 13 of the envelope 1 is then sealed to the cylindrical end 5 of the cone 3. A rectangular flat mirror plate 17 is then provided on the rectangular end 7 of the cone 3 and forms the screen 15 of the envelope 1.

It is possible in a very simple and cheap manner to manufacture, by means of the method according to the invention, envelopes having a diversity of dimensions and shapes of which the manufacture with the methods known so far and in particular of smaller numbers, is associated with very high costs.

What is claimed is:

l. A method of manufacturing envelopes for oscillograph cathode ray tubes having a flat screen portion, a cone portion and a tubular neck portion, comprising the steps of cutting from a glass plate the screen portion and, respectively, planar elements each having a periphery corresponding substantially to the periphery of an axial section of said cone portion, cutting a glass tube into lengths for said neck portion, positioning the planar elements on'a convex mold, heating the planar elements and the mold until the elements sag around the mold and engage the surface thereof, cooling the pre-shaped elements to room temperature, welding the pre-shaped elements together to form a cone, and welding the neck portion to one end and the screen portion to the other end of said cone portion.

2. A method according to claim 1, wherein said one end of said cone and said tubular neck portion having substantially circular cross-sections, and said other end of said cone and said screen portion have substantially rectangular cross-sections.

3. A method as claimed in claim 1, characterized in that for welding two pre-shaped elements together they are centered in a mould relative to each other in such manner that their edges to be welded together contact each other, after which the edge portions of the elements are heated by means of burners until the glass edge portions become electrically conductive, after which they are further heated by means of thermal energy caused by the Joule effect until the edges are sealed together, the resulting cone being then cooled.

4. A method as claimed in claim 3, characterized in that the pre-shaped elements during welding together are moved relative to each other in a direction normal to their edges to be welded together. 

1. A METHOD OF MANUFACTURING ENVELOPES FOR OSCILLOGRAPH CATHODE RAY TUBES HAVING A FLAT SCREEN PORTION, A CONE PORTION AND A TUBULAR NECK PORTION, COMPRISING THE STEPS OF CUTTING FROM A GLASS PLATE THE SCREEN PORTION AND, RESPECTIVELY, PLANAR ELEMENTS EACH HAVING A PERIPHERY CORRESPONDING SUBSTANTIALLY TO THE PERIPHERY OF AN AXIAL SECTION OF SAID CONE PORTION CUTTING A GLASS TUBE INTO LENGTHS FOR SAID NECK PORTION, POSITIONING THE PLANAR ELEMENTS ON A CONVEX MOLD, HEATING THE PLANAR ELEMENTS AND THE MOLD UNTIL THE ELEMENTS SAG AROUND THE MOLD AND ENGAGE THE SURFACE THEREOF, COOLING THE PRESHAPED ELEMENTS TO ROOM TEMPERATURE, WELDING THE PRE-SHAPED ELEMENTS TOGETHER TO FORM A CONE, AND WELDING THE NECK PORTION TO ONE END AND THE SCREEN PORTION TO THE OTHER END OF SAID CONE PORTION.
 2. A method according to claim 1, wherein said one end of said cone and said tubular neck portion having substantially circular cross-sections, and said other end of said cone and said screen portion have substantially rectangular cross-sections.
 3. A method as claimed in claim 1, characterized in that for welding two pre-shaped elements together they are centered in a mould relative to each other in such manner that their edges to be welded together contact each other, after which the edge portions of the elements are heated by means of burners until the glass edge portions become electrically conductive, after which they are further heated by means of thermal energy caused by the Joule effect until the edges are sealed together, the resulting cone being then cooled.
 4. A method as claimed in claim 3, characterized in that the pre-shaped elements during welding together are moved relative to each other in a direction normal to their edges to be welded together. 